when i think of insulation (and it doesn’t happen very often), those pink fiberglass batts come to mind. we don’t have any insulation (none, not one shred) yet, but adding some is pretty high on the reno list. it would be great to find a budget and eco-friendly option, so i decided to investigate.

First off: R-value. All insulation is rated by R-value which relates to how well it insulates. The higher the number, the greater the thermal resistance. Pink fiberglass has an R-value of about 3.5 per inch.

Secondly: environmental considerations.

What is the insulation made of? I’d prefer to stay away from materials that use petrochemicals, or other hazardous/damaging substances in their manufacture.

What is the fire resistance of the insulation? Certain materials like polystyrene are highly flammable, which means they are either treated with toxic anti-flammability agents or require an additional layer of some fire-rated material. Also, some types of insulation emit highly toxic gases when they catch on fire, which doesn’t sound very good. of course, neither does having a fire, but it would be nice if it was the least-damaging kind of fire, if you know what i mean.

Are there issues with longevity of materials? For instance, open-cell spray foam insulation settles over time, diminishing its R-value significantly. Is there off-gassing as the materials age? Are there issues with mold? Blown cellulose has the reputation (perhaps undeservedly) of being prone to mold, and i live in a very damp climate.

Thirdly: practicality.

We need a material that is relatively easy to source and install and that is affordable. Is it a DIY or do you need to call in the professionals? it could be the most green option in the world, but if it costs three times what fiberglass insulation does, there is no way I can justify it with our budget.

the big box stores offer fiberglass, rigid polystyrene, and mineral wool insulation (Roxul). Of the three, fiberglass is clearly the worst. the mineral wool is reportedly easier to install than fiberglass, it is made from a mix of recycled steel slag and basalt rock instead of petrochemicals (like styrofoam) and it is highly fire-resistant. the downside is that you need to take the same precautions during installation as with fiberglass due to air-borne fibers that are irritating and potentially carcinogenic, and you still need to install a vapour barrier. Mike Holmes (think Bob Vila on steroids) likes to start with rigid polystyrene on exterior walls, because then you don’t need a vapour barrier (the styrofoam acts as a thermal break). He suggests gluing it right to your basement walls before studding, and then (based on the pictures) insulating between the studs after that.

denim insulation (Ultratouch) is made from 85% post-industrial recycled fibers treated with boron (relatively low-toxic) as a fire and mold retardant. it is easy to install, non-toxic, doesn’t off-gas, and looks good on everyone! the r-value is as good or better than fiberglass. the downside is cost and availability. i did find a local distributor, but cost is definitely an issue – comparing r-21 rated denim insulation to r-22 rated mineral wool, the price is almost double – $1.60/square foot for the denim vs. $0.87/square foot for the mineral wool.

sheep’s wool insulation (good shepherd) has the same benefits as denim insulation, without the recycled content. seems to be more widely available in the U.K. pricing is absolutely bewildering – batts are cost at $6.50/pound.

blown cellulose seems like a reasonably green option. it is made largely from recycled materials (newspaper, cardboard, cotton, etc.) treated with boric acid as a fire and mold retardant. based on your application, loose fill is blown into the space where you need insulation (attic, retro-insulating walls). Some settling of materials (up to 20%) will occur and the resulting R-value is slightly lower than fiberglass insulation. The downside (to me) seems to be that you need professionals to install it, and it wouldn’t it be really messy if you needed to go up into the attic for anything? There are low dust and wet spray options, but this may not be the best solution for those sensitive to dust from newsprint or paper.

icynene foam is something that i’d read about in a dwell reno story. it is a form of spray polyurethane foam insulation blown in with water that doesn’t release harmful polybrominated diethyl ethers (PBDEs). professional installation required, and reportedly expensive. the upside of the product is that it doesn’t emit VOCs and is a very effective insulator, especially in retrofits where it expands to fill nooks and crannies. Manufacturers have recently introduced ICYNENE LD-R-50™ which is partially made with castor oil. There is an intelligent discussion about icynene here. also, the first LEED Platinum home remodel in the U.S. used styrofoam and spray polyurethane foam products.